The present invention relates to a material for electron beam writing apparatus for forming very fine patterns with high precision, and more particularly to a material for a holder for supporting semiconductor chips used in electron beam writing apparatus.
The integration degree of IC has rapidly been densified and developed toward a real age of super LSI or very large scale integrated, while each kind of fine pattern forming techniques has been developed actively.
Among these techniques, an electron beam writing apparatus excels other methods in small minimum dimension of beams, writing speed and cost.
In the fine pattern forming techniques, however, it is necessary to limit a pattern line width to less than 1.0 .mu.m and writing precision to less than 0.1 .mu.m, and the material is further required to have an extremely small dimension change due to temperature and non-magneticity and more particularly good conductivity in the case of work stage system. The reason why the non-magnetism is required is because if a magnetic field is generated in the electron beam writing apparatus, a dimension change, disturbance and absorption of electron beams due to magnetostriction are produced to make the apparatus unusable.
As material for electron beam writing apparatus, use is exclusively made of high Al alloy close to pure Al, and this alloy is preferable in the point of having non-magnetism and good conductivity, but its thermal expansion coefficient is large such as 23.times.10.sup.-6, so that in order to avoid a slight dimension change due to temperature in use, a temperature should strictly be controlled to .+-.0.1.degree. C. particularly in work stage and lens systems. However, even if the temperature control is strictly managed, in the case of a cassette for holding a stage system or mask, it is difficult to prevent a temperature rise due to heat generation during writing with electron beams.
There has not been known any material, satisfying all the three properties, non-magneticity, small thermal expansion coefficient and good thermal conductivity, for semiconductor holder used in the electron beam writing apparatus.